Process dependence of hot carrier degradation in PMOSFETS

The dual-poly-gate is widely used in today´s advanced technologies. B penetration through the PMOSFET gate oxide from the P⁺-gate during high-temperature annealing decreases the oxide lifetime due to the generated positive charge. To overcome the B penetration, gate oxide nitridation is widely used in this process step. Nitridation not only prevents B penetration, but also increases the hot carrier performance on NMOS. However, the hot carrier performance on PMOS is reported to be severely worse at Vg=Vd. Besides the NO anneal, the gate and source/drain implantation species are also changed. BF₂ is widely used in the shallow junction process. It is reported that F can enhance the B diffusion on the gate oxide. The new process steps impact the PMOSFET hot carrier reliability, which is one of the long-term reliability concerns for VLS circuits. In this paper, the worst-case stress conditions and impact of NO anneal and F on PMOSFET hot carrier reliability are investigated.